IPv4 Free Pool of Addresses Hits Zero for U.S. and Canada

The American Registry for Internet Numbers (ARIN) announced today that its free pool of IPv4 addresses has hit the "zero" level.

The announcement signifies greater difficulty for organizations trying to get IPv4 Internet addresses within ARIN's service area, which includes the United States and Canada, as well as Caribbean and North Atlantic islands. Organizations responsible for overseeing the distribution of IPv4 Internet addresses have long warned that the demand for IPv4 addresses has been outstripping supply. However, getting Internet service providers and equipment manufacturers to switch over to the current IPv6 protocol has been a slow process.

ARIN is one of the five Regional Internet Registries (RIRs) that get its Internet addresses from the Internet Assigned Numbers Authority (IANA), which is a department of the Internet Corporation for Assigned Names and Numbers (ICANN). ICANN highlighted the IPv4 shortage last year when it was compelled to ship recovered addresses to one of the RIRs. IANA had issued its last IPv4 address blocks to the RIRs' free pools back on Feb. 3, 2011, per ARIN's timeline.

While ARIN's free pool of IPv4 addresses has run out, it still handles returned or reclaimed addresses, as well as addresses that were revoked due to nonpayment. However, ARIN must follow specific rules on the day when it runs out of IPv4 addresses. Specifically, it has to fill waiting-list requests for IPv4 addresses before adding IPv4 addresses to its free pool.

Here's how ARIN describes its operating procedures, going forward:

In the future, any IPv4 address space that ARIN receives from IANA, or recovers from revocations or returns from organizations, will be used to satisfy approved requests on the Waiting List for Unmet Requests. If we are able to fully satisfy all of the requests on the waiting list, any remaining IPv4 addresses would be placed into the ARIN free pool of IPv4 addresses to satisfy future requests.

ARIN now must now allocate IPv4 addresses into a "single, continuous range of addresses," according to its IPv4 Depletion FAQ. It can't fulfill requests that are larger than this range. The size of that range wasn't specified in the FAQ, but organizations could find out that they are requesting blocks of addresses that are too large for ARIN to fill.

If ARIN's customers don't want to use its waiting list to get IPv4 addresses, then they can engage in the IPv4 transfer market. Essentially, under this scheme, an organization agrees to transfer a block of IPv4 addresses to another organization, which gets facilitated via the ARIN Online site.

IPv4 supports about 4.3 billion IP addresses but it can't expand because it's a 32-bit protocol. The current IPv6 standard is a 128-bit protocol that's estimated to support "340 trillion trillion trillion" IP addresses.

There can be transitional issues as organizations switch to IPv6. A voluntary 24-hour test of IPv6 in 2011 organized by the Internet Society, called "World IPv6 Day," highlighted some of those issues. The Internet Society advocates that ISPs and Web companies update their networks to support IPv6. Hardware manufacturers should update their firmware to support it as well, according to an Internet Society FAQ.